1. Field of Invention
This invention relates to an optical device incorporating a plurality of optical parts (elements), and to a projection display device including this optical device.
2. Description of Related Art
In a projection display device, in order to increase the usage efficiency of light and obtain a bright projected image, a polarized light illumination optical system and an integrator optical system are utilized. The polarized light illumination optical system is an optical system which utilizes only polarized light having one polarization direction as illuminating light. In this polarized light illumination optical system, a polarizing conversion element for converting non-polarized light (light having random polarization directions) into light having one polarization direction is employed. In addition, the integrator optical system is an optical system which divides light source light into a plurality of fine partial luminous fluxes, and which utilizes the respective partial luminous fluxes as illuminating light. In this integrator optical system, a lens array that includes a plurality of small lenses and that divides light source light into a plurality of partial luminous fluxes is employed. An illumination optical system is normally constructed by a combination of the polarized light illumination optical system and the integrator optical system.